Lowercase extensions too, dynamically change when we try to create thumbnails by memory limit.

git-svn-id: https://develop.svn.wordpress.org/trunk@6783 602fd350-edb4-49c9-b593-d223f7449a82

wp-includes/functions.php

@@ -1070,7 +1070,7 @@ function wp_unique_filename( $dir, $filename, $unique_filename_callback = NULL )
 
 	// separate the filename into a name and extension
 	$info = pathinfo($filename);
-	$ext = $info['extension'];
+	$ext = strtolower( $info['extension'] );
 	$name = basename($filename, ".{$ext}");
 
 	// Increment the file number until we have a unique file to save in $dir. Use $override['unique_filename_callback'] if supplied.